Engine Braking & Neutral Coasting: Gas Mileage Tested

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VIAN

Diamond Member
Aug 22, 2003
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I've read Neutral Coasting is bad, illegal, unsafe... and that it doesn't save you gas. I agree that it is unsafe, but does it really not save any gas? I've also read that Engine Braking doesn't have an effect on gas mileage. I'll be testing both theories to try and give people some concrete data.

The car I used for the tests is my 2003 Toyota Corolla S. The gas mileage was attained by dividing the mileage at the point the gas light comes on by ten gallons. Whenever I fill up the car when the light comes on, I only fill up about ten. It's not a perfect system, but the results should be within the ballpark. As far as driving conditions go: I've been driving through many different conditions every day before these test and I always used to get similar gas mileage.

My normal driving habits:

City Acceleration <= 3000 rpm
City Cruise <= 2000 rpm

Highway Acceleration <= 3000 rpm, sometimes, though, I go all the way to 6000 rpm for fun
Highway Cruise <= 3000 rpm

Engine braking <= 2000 rpm

Driving with these limits I get 28.5 mpg. This will be the reference gas mileage.


Neutral Coasting + low rpm acceleration driving habits:

City Acceleration <= 2000 rpm
City Cruise <= 2000 rpm

Highway Acceleration <= 3000 rpm
Highway Cruise <= 3000 rpm

Engine Braking = 0

Driving with these limits I get 35 mpg. That's a 23% increase over the reference. Bascially, if I'm not accelerating, the car is in neutral. It saves a lot of gas, but it requires a lot of shifting and takes the fun out of driving; as well as being less safe.


High rpm engine braking driving habits:

City Accleration <= 3000 rpm
City Cruise = 1600 - 2600 rpm, (arbitrary number that previously had importance, but no longer)

Highway Acceleration <= 3000 rpm, sometimes though I go all the way to 6000 rpm for fun
Highway Acceleration <= 3000 rpm

Engine Braking <= 3000 rpm, and sometimes at <= 4000 rpm

Driving with these limits I get 27.5 mpg. That's a 3.5% decrease in gas mileage over the reference. However, it's probably attributed more to the city cruise rpms being higher than in my normal driving habits. So, engine braking uses negligible gas, if any.
 
R

randay

Lifer
May 30, 2006
11,018
216
106
Originally posted by: VIAN
I've read Neutral Coasting is bad, illegal, unsafe... and that it doesn't save you gas. I've also read that Engine Braking doesn't have an effect on gas mileage. I've been testing each theory with my 2003 Toyota Corolla S.

Normal Driving engine speeds

City Acceleration <= 3000 rpm
City Cruise <= 2000 rpm

Highway Acceleration <= 3000 rpm, sometimes though I go all the way to 6000 rpm for fun
Highway Cruise <= 3000 rpm

Driving with these limits I get 29 mpg. Sometimes I engine break with engine speed of 2000 rpm. Sometimes I cruise in neutral.


Extreme Neutral Coasting engine speeds

City Acceleration <= 2000 rpm
City Cruise <= 2000 rpm

Highway Acceleration <= 3000 rpm
Highway Cruise <= 3000 rpm

Driving with these limits I get 35 mpg. Bascially, if I'm not accelerating the car it is in neutral. It saves a lot of gas, but it takes a lot of shifting and you give up the fun of high acceleration.


Extreme Engine Braking engine speeds

City Accleration <= 3000 rpm
City Cruise = 1600 - 2600 rpm, if there is an emergency, these speeds will allow me some useful acceleration

Highway Acceleration <= 3000 rpm, sometimes though I go all the way to 6000 rpm for fun
Highway Acceleration <= 3000 rpm

Driving with these limits I get 27.5 mpg. I've engine braked almost all the time with the engine speed of 3000 rpm, and sometimes 4000 rpms. This requires a lot of shifting to keep within the city cruise; because of that you also need to keep looking at the tachometer. The shifting isn't smooth when engine breaking at those kind of engine speeds. I had to rev up the engine in preperation for smooth shifting, that probably does a number on the clutch.


Overall, I think Normal Driving is much more fun and relaxing, while not giving up complete loss of control.
Click to expand...

Probably effectively negating any fuel savings gained by engine breaking.
 
J

jagec

Lifer
Apr 30, 2004
24,442
6
81
Ok, if you don't know how to properly engine brake, you won't save any fuel.
 
S

spidey07

No Lifer
Aug 4, 2000
65,469
5
76
DAGNABBIT!!!

Learn how to drive.

this has been discussed ad nauseum. learn how to freakin' drive
 
J

jagec

Lifer
Apr 30, 2004
24,442
6
81
Originally posted by: iversonyin
Originally posted by: jagec
Ok, if you don't know how to properly engine brake, you won't save any fuel.
Click to expand...

How do you engine brake properly?
Click to expand...

Well, unless you're racing, you shouldn't downshift into every single gear when you're coasting to a stop. Say you're going 30mph, in fourth gear or so. You see the light turn red ahead of you. Don't push in the clutch, don't downshift into third, then second, then first. Just take your foot off the gas, push gently on the brake, and when your RPMs drop to just above idle, THEN push in the clutch. If you were accelerating when you say the light turn, you might want to drop a gear, but don't stomp on the gas to match your revs, and slam it down. Be smooth. Come to a stop, shift into first. If you're on the freeway going 60 or so, same drill. Leave it in top gear, don't push in the clutch, just let the engine slow you down, or help it out a little with the brakes. Once you get to a low RPM, maybe downshift into second or third with a blip of the throttle, and keep slowing. The real secret to saving gas is anticipation...if you see traffic slowing ahead, don't carry all your speed until you're right behind them, then dump it with some hard braking. Take your foot off the gas, slow down as you're catching up. Half the time the traffic will start moving again, and you're able to save some momentum that you otherwise would have thrown away. Similarly, if you see a light that's been red for a while up ahead, start slowing down a bit earlier, and it might turn green before you have to touch the brakes. The less you touch the gas OR brakes, the better mileage you get. "Engine braking" applies to 2000RPM in fifth gear, just as much as 7000RPM in second.
 
AgaBoogaBoo

AgaBoogaBoo

Lifer
Feb 16, 2003
26,108
5
81
I didn't read the whole thread, but in city driving just use the brake pedal to slow down, why put extra wear and tear on the clutch when it's not needed? Brake pads are cheaper and easier to replace than a clutch.
 
P

Pacfanweb

Lifer
Jan 2, 2000
13,155
59
91
Dude, you can't drive.
What's with all the acceleration stuff? Engine braking or neutral braking is irrelevant to acceleration.

All engine braking is, is downshifting and letting the engine slow the car instead of kicking it up into neutral and using the brakes.

That's it.
 
J

jagec

Lifer
Apr 30, 2004
24,442
6
81
Originally posted by: AgaBoogaBoo
I didn't read the whole thread, but in city driving just use the brake pedal to slow down, why put extra wear and tear on the clutch when it's not needed? Brake pads are cheaper and easier to replace than a clutch.
Click to expand...

WHAT wear and tear on the clutch? First off, a good clutch should last for >100,000 miles. Second, if you're burning your clutch every time you change gears, you're doing it wrong. Third, you don't have to slam it down three gears to take advantage of engine braking, just leave it in gear and use your brakes as well, only pressing the clutch once you're almost stopped.
 
V

VIAN

Diamond Member
Aug 22, 2003
6,575
1
0
Originally posted by: jagec
Ok, if you don't know how to properly engine brake, you won't save any fuel.
Click to expand...
In the city, during the high rpm engine braking mode, I would cruise on the 3rd gear, and then shift to 2nd gear when stopping. On the highway, I'd be in the 5th gear, then, after lowering my engine speed, shift to the 3rd gear and then to the 2nd gear. If I was on the highway on the 4th gear, then I may just shift to the 2nd gear.

What I mean when I rev up is that I hold the clutch midway till the engine speed is near matching. Then I cruise in the 2nd gear, letting the engine stop me and I release the gear just before I stop. Just like you say, save momentum.

Originally posted by: Pacfanweb
Dude, you can't drive.
What's with all the acceleration stuff? Engine braking or neutral braking is irrelevant to acceleration.

All engine braking is, is downshifting and letting the engine slow the car instead of kicking it up into neutral and using the brakes.

That's it.
Click to expand...
The point of the OP is to show you the engine speeds of how I drive, then the summary at the bottom is what I did as I was driving that way. Normal Driving, Extreme Neutral Coasting, and Extreme Engine Braking are just 'modes' of driving. This lets you know my driving habits while I was testing the neutral coasting and engine braking so that it's documented that I wasn't flooring it to the max in different modes to make my arguement better.
 
B

blahblah99

Platinum Member
Oct 10, 2000
2,689
0
0
I usually use engine braking if I am coasting because my ECU actually turns off the injectors (as in doesn't squirt fuel into the cylinders) when I have my foot off the gas pedal and the engine RPM is greater than around 1500RPM.
 
F

FrustratedUser

Lifer
Aug 16, 2001
22,505
4
81
Originally posted by: jagec
Originally posted by: iversonyin
Originally posted by: jagec
Ok, if you don't know how to properly engine brake, you won't save any fuel.
Click to expand...

How do you engine brake properly?
Click to expand...

Well, unless you're racing, you shouldn't downshift into every single gear when you're coasting to a stop. Say you're going 30mph, in fourth gear or so. You see the light turn red ahead of you. Don't push in the clutch, don't downshift into third, then second, then first. Just take your foot off the gas, push gently on the brake, and when your RPMs drop to just above idle, THEN push in the clutch. If you were accelerating when you say the light turn, you might want to drop a gear, but don't stomp on the gas to match your revs, and slam it down. Be smooth. Come to a stop, shift into first. If you're on the freeway going 60 or so, same drill. Leave it in top gear, don't push in the clutch, just let the engine slow you down, or help it out a little with the brakes. Once you get to a low RPM, maybe downshift into second or third with a blip of the throttle, and keep slowing. The real secret to saving gas is anticipation...if you see traffic slowing ahead, don't carry all your speed until you're right behind them, then dump it with some hard braking. Take your foot off the gas, slow down as you're catching up. Half the time the traffic will start moving again, and you're able to save some momentum that you otherwise would have thrown away. Similarly, if you see a light that's been red for a while up ahead, start slowing down a bit earlier, and it might turn green before you have to touch the brakes. The less you touch the gas OR brakes, the better mileage you get. "Engine braking" applies to 2000RPM in fifth gear, just as much as 7000RPM in second.
Click to expand...

Finally someone who actually has a clue.
This is the very first basics of driving everyone learns during the first 3 driving lessons in most any country in Europe.
Basic stuff folk..... why do you guys insist on discussing this.... damn. Sorry, I forgot 90% of all cars in the US is automatic.
 
S

SophalotJack

Banned
Jan 6, 2006
1,252
0
0
Anyone else point out that given the fact that the OP gets ~28 mpg means he has a cheapo shat car anyhows and this thread is pointless?

Get a real car and do your "experiments" on it, OP. You might actually have some valuable info at that point... you know, for real cars that benefit from engine braking and such.


P.S. you are a cheapass.... I just noticed your sig.... cheapass

edit: you also don't know how to drive (finished reading your OP in detail)
 
S

Suspicious-Teach8788

Lifer
Feb 19, 2001
20,155
23
81
Originally posted by: SophalotJack
Anyone else point out that given the fact that the OP gets ~28 mpg means he has a cheapo shat car anyhows and this thread is pointless?

Get a real car and do your "experiments" on it, OP. You might actually have some valuable info at that point... you know, for real cars that benefit from engine braking and such.


P.S. you are a cheapass.... I just noticed your sig.... cheapass

edit: you also don't know how to drive (finished reading your OP in detail)
Click to expand...

Dude shut up, your own data that you pull out of your own @$$ is not any better, so do not just insult the OP. WHo cares if he is some cheapo? We all want to save money. That's great if you like to throw cash out the window.
 
G

goodoptics

Platinum Member
Aug 18, 2000
2,652
0
0
Originally posted by: spidey07
DAGNABBIT!!!

Learn how to drive.

this has been discussed ad nauseum. learn how to freakin' drive EFFICIENTLY!
Click to expand...
Fixed.


Originally posted by: jagec
Originally posted by: iversonyin
Originally posted by: jagec
Ok, if you don't know how to properly engine brake, you won't save any fuel.
Click to expand...

How do you engine brake properly?
Click to expand...

Well, unless you're racing, you shouldn't downshift into every single gear when you're coasting to a stop. Say you're going 30mph, in fourth gear or so. You see the light turn red ahead of you. Don't push in the clutch, don't downshift into third, then second, then first. Just take your foot off the gas, push gently on the brake, and when your RPMs drop to just above idle, THEN push in the clutch. If you were accelerating when you say the light turn, you might want to drop a gear, but don't stomp on the gas to match your revs, and slam it down. Be smooth. Come to a stop, shift into first. If you're on the freeway going 60 or so, same drill. Leave it in top gear, don't push in the clutch, just let the engine slow you down, or help it out a little with the brakes. Once you get to a low RPM, maybe downshift into second or third with a blip of the throttle, and keep slowing. The real secret to saving gas is anticipation...if you see traffic slowing ahead, don't carry all your speed until you're right behind them, then dump it with some hard braking. Take your foot off the gas, slow down as you're catching up. Half the time the traffic will start moving again, and you're able to save some momentum that you otherwise would have thrown away. Similarly, if you see a light that's been red for a while up ahead, start slowing down a bit earlier, and it might turn green before you have to touch the brakes. The less you touch the gas OR brakes, the better mileage you get. "Engine braking" applies to 2000RPM in fifth gear, just as much as 7000RPM in second.
Click to expand...
QFT!


I engine brake in 5th and 3rd when driving around town.
Also, hook up a vacuum gage to the intake manifold to monitor the intake vacuum and a steady right foot will help achieve good mileage, too!
 
E

Eos

Diamond Member
Jun 14, 2000
3,463
17
81
Learn to float between gears and your clutch concerns are out the window.
 
J

jagec

Lifer
Apr 30, 2004
24,442
6
81
Originally posted by: SophalotJack
Anyone else point out that given the fact that the OP gets ~28 mpg means he has a cheapo shat car anyhows and this thread is pointless?

Get a real car and do your "experiments" on it, OP. You might actually have some valuable info at that point... you know, for real cars that benefit from engine braking and such.


P.S. you are a cheapass.... I just noticed your sig.... cheapass
Click to expand...

While 28 mpg is a strange figure, hovering between a true economy car at mid-30s and a sporty sedan at low 20s, there are certainly decent cars that get such mileage.

As for cheap, I AM a cheapass and I can tell you that 15% is NOT below the cheapass line. 10% is standard IMHO;)
 
V

VIAN

Diamond Member
Aug 22, 2003
6,575
1
0
I revised the OP, it may be easier to understand. Also the conclusion has changed. Previously, I was trying to see what saved more gas, normal driving, extreme engine breaking, or extreme neutral coasting + low rpm acceleration. But, then I realized that this wasn't what I was trying to answer.

What I needed to answer was: Doesn't neutral coasting save gas? & Does engine breaking waste gas?
 
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